Present-day corn and soy bean combines are typically provided with one or more foraminous cleaning platforms or "shoes" which, when reciprocated or shaken rapidly while a strong current of air is passed upwardly through the shoe and along its upper surface, is capable of fairly effectively separating heavier grain particles from lighter chaff and trash materials. The heavier materials resist entrainment in the airstream and gravitate through apertures in the cleaning shoe for collation and temporary storage in a collection chamber on the combine, while the lighter chaff particles become airborne and are carried from the top surface of the cleaning shoe toward the rear of the combine for discharge.
Combining on sidehill slopes presents a number of problems, among which is the natural tendency for crop materials deposited on the cleaning shoe to gravitate toward the downhill side of the combine and thus accumulate disproportionately along the downhill sidewall of the cleaning shoe, instead of spreading fairly evenly over the entire surface area of the cleaning shoe as in normal, flat land combining. As a result of such excessive, localized accumulation of materials, airflow upwardly through the shoe and along the top surface thereof is impeded, to the end that desirable grain particles may be shaken off the end of the shoe and discharged along with trash and chaff particles instead of passing down through the shoe in the intended manner. Depending of course upon the extent of the farmer's acreage devoted to sidehill slopes or terraces, the grain losses incurred can be quite significant and costly, particularly considering the farmer's need to be as efficient and productive as possible in order to realize a net return on the relatively high capital costs involved in modern farming operations.
As is well known by those skilled in the art, some combines are conventionally provided with hydraulic levelling mechanisms that permit the harvesting header of the machine to remain tilted according to the sidehill slope while the operator cab, grain cleaning apparatus and storage tank are adjustably rotated about a fore and aft axis relative to the header to such an extent that those portions of the machine remain fairly level. Thus, among other things, the materials which collect on the cleaning shoes for separation and cleaning are spread out relatively evenly and the cleaning action can be carried out relatively efficiently. However, such selectively tiltable, hydraulic levelling systems are quite expensive and are thus financially beyond the reach of many who would perhaps seriously be in need of such features.
Additionally, certain conventionally existing combines are provided with so called "lift-out chaffer sections" located on each side of the chaffer at the back of the combine which, when removed, cause crop that builds up on the downhill side of the cleaning shoe to be captured and routed back to the initial cleaning cylinder. However, not all combines are provided with such lift-out sections and, moreover, such construction does not entirely solve the grain loss problems when harvesting sidehill slopes.